The present invention relates to a tube joint for use with a multi-walled tube assembly, and more particularly to a tube joint capable of joining a multiwalled tube assembly composed of a plurality of coaxial tubes for introducing and discharging a fluid, easily to a fluid-pressure-operated device such as a solenoid-operated valve, a cylinder, or the like, and of preventing the multi-walled tube assembly from being damaged at the time of connecting the same to and disconnecting the same from the tube joint.
Fluid-pressure-operated devices have widely been used to drive objects under air pressure, for example. Such a fluid-pressure-operated device has a plurality of ports for introducing and discharging air, and tubes are connected to such ports.
The tubes for introducing air into and discharging air from the ports are put together as closely as possible in order to allow the tubes to be installed in a small space and to facilitate the maintenance of the tubes. One specific tube arrangement is illustrated in FIG. 1 of the accompanying drawings. A fluid-pressure-operated device 2 has first and second ports 4, 6 defined therein and connected to respective tubes 8, 10 through first and second tube joints 12, 14. The first and second tube joints 12, 14 are threaded respectively in the first and second ports 4, 6, and the tubes 8, 10 are fitted respectively over joint tube members 16, 18 integral with the first and second tube joints 12, 14.
The tubes 8, 10 are bundled together by a string or band 20 so that they can be installed in a small space and can easily be maintained or serviced. Where a fluid-pressure-operated device such as a manifold-type solenoid-operated valve has many output ports, however, many tubes have to be connected thereto, and the entire arrangement is complex. Since the tubes are bundled together by the string or band 20 at several locations, a considerable number of steps are required to tighten all strings or bands 20. As more and more tubes are to be connected, the number of installing steps is increased, and so is the danger of interconnecting wrong ports with the tubes.
In case a fluid-pressure-operated device has many ports, it may be difficult to fasten the tubes with bands or strings dependent on the positions of the ports of the device. When a plurality of tubes are bundled by a string or a band, the pitch or distance between the tubes is so small that it will be practically difficult to connect the tubes to the tube joints in the process of joining the tubes to the device through the tube joints. The number of tube joints used is increased, resulting in an increase in the number of steps of installing the tubes.
Since the tubes and the tube joints are completely coupled to each other, the inner wall surfaces of the tubes may be damaged when the tubes are contracted and expanded due to a change in the fluid pressure in the tubes or a change in the temperature of the fluid.